Silica – what it is, properties and uses - Blog

As long as 4,000 years ago, craftsmen in Mesopotamia were using silica-rich sand to produce the first glassware. The vessels and ornaments produced in this way were initially luxury goods. Today, silica is used not only in glass production, but also in the food, cosmetics and pharmaceutical industries. It is an ingredient in many commonly used products, although its presence often goes unnoticed.

silica

What is silica and where is it found
What are the properties of silica?
What is silica used for?
Is silica safe for health?
FAQ – frequently asked questions about silica

What is silica and where is it found

Silica is a naturally occurring chemical compound, also known as silicon dioxide (SiO₂). It consists of two elements: silicon and oxygen. It is one of the most abundant minerals in the Earth’s crust. It is found primarily in sand, rocks and minerals, as well as in some living organisms.

One of the most common natural forms of silica is quartz, found, amongst other things, in granite, sandstone and quartz sand. Silicon dioxide is also the main component of amethyst and rock crystal. It can occur in various varieties, which differ in their internal structure, appearance and properties. Silica can also be produced using industrial methods that allow for control over particle size, structure and surface area. This results in materials designed for specific technological applications.

What are the properties of silica?

Pure silica is a solid substance which, depending on its form, can occur as a transparent crystal, a fine white powder or porous granules. It has no distinctive odour and is very slightly soluble in water. One of the characteristic features of silica is its high resistance to heat. Pure silicon dioxide melts at a temperature of approximately 1710°C. This makes it an important raw material for the production of glass and materials resistant to high temperatures.

Crystalline silica, particularly quartz, is also characterised by its high hardness. On the ten-point Mohs scale, quartz scores 7, meaning it can scratch glass and many other materials. Some forms of silica are characterised by a large surface area and a high number of fine pores. An example is silica gel, which can bind water vapour molecules to its surface. Fine-grained silica can also improve the flowability of powder mixtures by reducing the tendency of their components to clump together.

Occurrence and uses of silica

Category	Occurrence / application
Nature	Sand, quartz, granite
Construction	Concrete, mortar, glass, ceramics
Food	Spices, powdered mixes (E551)
Cosmetics and pharmaceuticals	Powders, foundations, toothpastes; tablets, capsules, supplements
Industry	Optical fibres, electronics, moisture absorbers

What is silica used for?

capsules

Silica is a key raw material in the production of glass, ceramics, building materials and optical fibres. Quartz sand is also used in the manufacture of concrete, mortar and abrasives.

In the food industry, synthetic amorphous silica is used as the additive E551. It prevents free-flowing products from caking and makes them easier to pour. It is used, amongst other things, in selected spices, food mixes and powdered preparations. In cosmetics, silica absorbs excess sebum, improves texture and provides a matt finish. It is used in powders, foundations and creams, and some varieties are abrasive ingredients in toothpastes.

In the pharmaceutical industry, it is used as an excipient in the production of tablets, capsules and dietary supplements. It improves the flowability of powdered mixtures, making them easier to dispense. Silica gel, on the other hand, is used to absorb moisture. Sachets containing it are placed, amongst other things, in the packaging of footwear, electronic goods and leather goods.

Is silica safe for health?

The safety of silica depends on its form, quantity and route of exposure. In 2024, the European Food Safety Authority (EFSA) concluded that the use of additive E551 in the products and quantities assessed did not raise any safety concerns for consumers. However, it highlighted the need for further research into the smallest silica particles. The greatest risk stems from long-term inhalation of crystalline silica dust, which increases the risk of silicosis, chronic obstructive pulmonary disease and lung cancer. This primarily concerns occupational exposure, for example during the processing of building materials.

"Silica is one of the most widespread mineral compounds on Earth, and at the same time a component of many everyday products. It is found in glass, cosmetics, medicines and food. However, its safety depends on its form and the manner of contact with the body. The food additive E551 is one thing, but crystalline silica dust inhaled at work is quite another.” Łukasz Domeracki – Dietitian

FAQ – frequently asked questions about silica

What is silica?

Silica, or silicon dioxide (SiO₂), is a chemical compound consisting of silicon and oxygen. It occurs naturally in sand, quartz and rocks, amongst other things. It can take the form of crystals, a fine powder or porous granules.

What is silica used for?

Silica is used in the production of glass, ceramics, concrete and optical fibres. It is also an ingredient in cosmetics, toothpastes, tablets and certain food products. In the form of silica gel, it absorbs moisture from the environment.

What does E551 mean on a product label?

E551 is silicon dioxide used as a food additive. Its main purpose is to prevent free-flowing products, such as certain spices and powdered mixes, from caking.

Is silica in food harmful?

According to the EFSA’s 2024 assessment, the use of E551 under the conditions assessed does not raise any concerns regarding consumer safety. However, the Authority highlighted the need for further research, particularly into the smallest silica particles.

Why is silica added to cosmetics?

Silica can absorb excess sebum, reduce skin shine and improve the texture of cosmetics. It is therefore used in products such as powders and foundations. Some varieties also act as abrasive agents in toothpastes.

Are silica and silicon the same thing?

No. Silicon is a chemical element, whilst silica is its compound with oxygen. These terms are sometimes confused, but they do not refer to the same substance. Nor should the presence of silica in a supplement be equated with proven health benefits.

Is silica dust dangerous?

Yes, particularly with prolonged inhalation of fine crystalline silica dust. Such exposure can lead to silicosis and increase the risk of serious lung diseases, including lung cancer. The risk mainly concerns certain construction and industrial jobs.

What is in the sachets labelled ‘silica gel’?

It is a silica gel that absorbs moisture and protects products from damp. The sachets are placed, amongst other things, in boxes containing footwear and electronic goods. They are not intended for consumption and should be kept out of the reach of young children.

Does silica in supplements improve the condition of the skin, hair and nails?

The mere presence of silica in a supplement does not mean that the product effectively improves the condition of the skin, hair or nails. The sources cited primarily describe its properties, technological applications and safety, rather than the proven efficacy of such supplements.

Source:

Mebert, A. M., Baglole, C. J., Desimone, M. F., & Maysinger, D. (2017). Nanoengineered silica: Properties, applications and toxicity. Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association, 109(Pt 1), 753–770. https://doi.org/10.1016/j.fct.2017.05.054
EFSA Panel on Food Additives and Flavourings (FAF), Younes, M., Aquilina, G., Castle, L., Degen, G., Engel, K. H., Fowler, P., Frutos Fernandez, M. J., Fürst, P., Gürtler, R., Husøy, T., Manco, M., Mennes, W., Moldeus, P., Passamonti, S., Shah, R., Waalkens-Berendsen, I., Wright, M., Andreoli, C., Bastos, M., … Gundert-Remy, U. (2024). Re-evaluation of silicon dioxide (E 551) as a food additive in foods for infants below 16 weeks of age and follow-up of its re-evaluation as a food additive for uses in foods for all population groups. EFSA journal. European Food Safety Authority, 22(10), e8880. https://doi.org/10.2903/j.efsa.2024.8880
Morais, R. P., Hochheim, S., de Oliveira, C. C., Riegel-Vidotti, I. C., & Marino, C. E. B. (2022). Skin interaction, permeation, and toxicity of silica nanoparticles: Challenges and recent therapeutic and cosmetic advances. International journal of pharmaceutics, 614, 121439. https://doi.org/10.1016/j.ijpharm.2021.121439